The present invention relates to a white balance controlling device for determining whether a fluorescent light source illuminates a subject.
Numeral electronic cameras, such as electronic still cameras or video cameras, are generally equipped with automatic white balance controllers. Such an automatic white balance controller detects a color temperature of a light source illuminates a subject to be recorded and corrects image signals of three primary colors which are provided from image sensors, such as charge coupled devices (CCDs), according to the color temperature detected thereby.
If a fluorescent lamp is used to illuminate a subject, the brightness of the subject tends to be relatively low and the fluorescent lamp generally generates flickered light. As a result, the operation of the white balance controller is difficult. To avoid effects of flickered fluorescent light, a shutter should be controlled to operate at a speed slower than 1/60 sec. Therefore, it is necessary to determine whether a light source is illuminating a subject. One such light source determining device has been disclosed in Japanese Unexamined Patent Publication No. 61-240,790. The light source determining device disclosed in the Japanese Unexamined Patent Publication No. 61-240,790 detects fluorescent light that flickers according to the commercial frequency of 50 or 60 Hz. The light source determining device is, therefore, not available for fluorescent light sources that generate light flickering at commercial frequencies, which vary from country to country, other than 50 or 60 Hz or at a frequency of several hundred Hz. A white balance controller in cooperation with the light source determining device thus constructed is not effective for such non-commercial fluorescent light sources.